A dielectric porcelain composition is widely used in a high frequency region such as microwave or millimeter wave. As the characteristics required for these various applications, the followings can be cited. That is,
(1) since a wavelength is shortened to 1/∈r1/2 in a dielectric material, the relative dielectric constant ∈r is large in order to achieve miniaturization,
(2) the dielectric loss in a high frequency region is small, that is, the Qf value is high, and
(3) the temperature coefficient τf at a resonant frequency is small and stable.
Furthermore, it is important as well that the temperature coefficient τf is controllable in a predetermined range.
As such a dielectric porcelain composition for use in a high frequency region, many materials have been proposed. For instance, LnAlO3—CaTiO3-based dielectric porcelain (see patent literature 1) shows various dielectric characteristics depending on the composition thereof, and the characteristics such that, in a range where the relative dielectric constant ∈r is in the range of from 30 to 47, the Qf value is in the range of from 10,000 to 58,000 (value at 1 GHz) are obtained. However, although the Qf value is relatively high, the relative dielectric constant ∈r is low and the temperature coefficient τf is not so small; accordingly, there remains a problem in the application as practical devices.
In order to overcome the problems of the above-mentioned material, (1−x)Nd(Ga1-yAly)O3-xCaTiO3-based dielectric porcelain (see patent literature 2) has been proposed. This material has NdGaO3—CaTiO3 as a base composition, and when Ga is partially substituted by Al, the characteristics such that the relative dielectric constant ∈r is 45 or more and the Qf value is 43,000 or more are obtained, and the temperature coefficient τf can be controlled by varying a substation amount of Al.
Patent literature 1: Japanese Patent No. 2,625,074
Patent literature 2: JP-A-2002-274939